All ceramic denture and method of producing same



Feb. 15, 1.944. P, LEE r AL 2,341,998

ALL CERAMIC DENTURE AND METHOD OF'PRODUCING SAME Original Filed May 31,1939 3 Sheets-Sheet l Exmgswu Fl 5 l EXPANSION |N CoNTRAcTroN PERCENT OFORIGINALLENGTH INVESTMENT CRITIcALRANG-E DENTURE BASE AM BODY 00THCERAMIC 800v FREEZING POINT OF PLATE PORCELAI [00 200 500-400 500 600700 800 900 I000 "00 I200 I500 I400 I500 I600 TEMPERATURE -F.

' INVENTORS PYUNGTOO WILL/AM LEE AND CHARLES DIETZ ATTORN EY FeB. 15,1944.

E x A r suou CONTRACTION P. w. LEE EIIAL ALL CERAMIC DENTURE AND METHODOF PRODUCING S AME original'File d FIE-I- May 31, 1959 3 Sheets-Sheet 2EXPANSION IN PERCENT OF LASTER NV I00 200 300 400 500 600 700 800 900I000 "001200 I300 I400 I500 I600 GROG TER IAL 00TH RAMIC BODYTEMPERATURE- F.

ATTORNEY ORIGINAL LENGTQgg Feb; 15; 1944. w LEE ETAL 2,341,998

ALL CERAMIC DENTURE AND METHOD OF PRODUCING SAME Original Filed ma 'sl,1939 s Sheets-Sheet s FIG. 7.

- mvE 'rOns PYUNGTOO WILL/A 41. E E ev AND CHARLE'5-DIEIZ.-..,

ATTdRNEY Patented Feb. 15, 1944 2,3

A'LL CERAMIC DENTURE AND METHOD OF PRODUCING SAME yungtoo William Lee'and Charles Dietz, York, Pa, assignors to The Dentists Supply Company ofNew York, New York; N. Y., a corporation of New York Originalapplication May 31, 1939, Serial No; 276,644. Divided and thisapplication July 9, 1940, Serial No. 344,501

6 Claims. (Cl. 10635) This invention relates to denture base material,and particularly to material for use in ,the manufacture of all-ceramicdentures.

Thisapplicationis a division of our co-pendperature are substantiallyharmonious, an ordinary investment material could not be employed. Thisis due to the fact that the thermal contraction of the investmentmaterial through the aforesaid critical range differs greatly from thethermal contractions of the bodies invested and thereby seriouslyimpairs the finished denture, because of pressures, strains and .thelike.

Not only must the thermal contractions of the tooth ceramic body and thedenture base ceramic ing parentapplication, Serial No. 276,644, filed 5May 31, 1939, and entitled All ceramic denture body be harmoniousthroughout the critical base with teeth, process and materials forprorange, but the material in which the bodies are ducing same," issuedAugust 25, 1942, Patent No. invested must also have a thermalcontraction 08- through the critical range substantially identical Intheparent application, it is pointed out that, m with the thermalcontractions of the bodies inin the dental art, the moulding orattaching of vested. one vitreous body, such as an artificial tooth, to7 An object, therefore, of'the invention hereof is another body ofdifiernt composition, such as a to provide a denture base material, thethermal denture base, at a temperature lower than the contraction ofwhich, through the critical range, fusing temperature of the higherfusing body, 155 is harmonious with the thermal contractions of has notheretofore been successfully accomplished, the ceramic material formingthe teeth and of by others, although the theory has been adtheinvestment material. vanced, and claimed in dental literature and pat-Another object of the invention is to provide ent Specifications. adenture base material, the ingredients of which In practice, no oneheretofore has been able 3 are so proportioned that a graph of itslinear to produce such bodies of different composition, thermalcontraction between approximately the coeficients of expansion andcontraction of 1000 F. and room temperature is substantially which arealike, at least through the critical a straight line. range fromatmospheric temperature to the plas- Another object of the invention isto provide tic stage of the material of lower fusing tem- 95 a denturebase ceramic body of lower fusing temperature, and from that plastictemperature to perature than a tooth ceramic body and townatmospherictemp rat trol the composition of the denture base ceramic Althoughpatentees have claimed to have acbody as to ingredients and relativeproportions complished this result, in materials having the to insuresubstantially harmonious contraction same coefiicients of expansion andcontractiomin e and expansion curves for both bodies at least mostcases, no formulae for the materials have through the critical range.been given, which would give this result, or if According to theinvention, feldspar, amorphous formulae have been given, they have-beenfound silica and borax glass are compounded in such to be unsuccessfulin practice, andarticles, and proportions that a graph of the expansionand particularly dentures of this nature, have never 35 contraction ofsuch a compound through the been produced commercially. critical rangebetween approximately 1000 F. In practice, it has been found that, ifthe and room temperature is substantially a straight difference in thelinear expansions and contracline. tions of the bodies, such as theartificial tooth In the drawings, and denture base ceramic materials, isgreater 40 Figure 1 is a graph sheet having as abscissae than .001" perlinear inch at any point between degrees of temperature in Fahrenheitscale, and room temperature and the plastic stage or the as ordinateslinear expansion graded in thoulower fusing body, the bodies cannot beunited sandths of an inch, the thermal expansions of by fusion withoutproducing checks and cracks the novel tooth ceramic body, the noveldenture in one or the other, or both such bodies. 46 ceramic body andthe contraction of the novel We have found thatafter a tooth c mi b yinvestment material have been graphically d a denture base ceramic yhave been p plotted from readings indicated on the most acduced whereinthe thermal contractions of both curate known scientific instrument forthis purbodies through the critical range from the plastic pose, stageof the lowerfusing body to room tom--50 Figure 2 is a similar sheet anddepicts the thermal expansion curves of two commercial investmentmaterials of general use, ordinaryfeldspar, the thermal contractioncurve of the novel investment material, and the thermal contractioncurve of the novel tooth ceramic material,

, silica.

Figure 3 is a plan view of a denture base model invested in one half ofan investment flask and shows a temporary denture base with teethattached applied to said model,

Figure 4 is a cross-sectional view along the line 44 of Figure 3,

Figure 5 is a view similar to Figure 4 showing the other half of theflask applied and the temporary-denture with teeth invested therein,

Figure 6 is a similar view showing the flask inverted and separated andthe temporary denture base removed, I

Figure '7 is a like view showing the novel denture base ceramic bodyresiding in the space formerly occupied by the temporary denture base,and the'fiask parts re-united, and

Figure 8 is a like view showing the relation of parts after fusion ofthe denture base ceramic body.

In Figure 1, the thermal expansion and contraction curve for the toothceramic body is shown by a full light line and marked Tooth ceramicbody. The common and principal ingredients from which artificialporcelain teeth are usually produced are feldspar, kaolin and Theirproportions may ceramic body for the artificial teeth giving the thermalexpansion and contraction curve shown in Figure 1, we have devised aformula as differ. As a follows:

. Per cent Feldspar '70 to 90 Amorphous silica 10 td 30 The teeth ofthis ceramic body may be manufactured either for general commercial usecontaining the usual dental pins, either of base or precious metal, ormay be provided with other means for fastening them to usual andordinary denture bases. For the purpose of this invention,

. all such fastening devices may be eliminated, and

we shall hereafter refer to teeth without any of these fastening devicesas bare teet In the prior art, numerous ceramic bodies for formingdenture bases have beendiscussed. It

has, however, been found that none of the disportant that thecontraction curves be in agreement from the softening point of thedenture base material down through the hardening range to roomtemperature in order that no cracking may occur, and in order that aperfect union between the two ceramic bodies may be effected;

The softening, maturing or fusing point of the denture base material maybe considerably lower than the fusing point of the tooth material. Thefusing point of the tooth material may be from approximately 2300 to2400 F. while the fusin point of the denture base material may be fromapproximately 1500 to 1600 F. Consequently, the ceramic body of whichthe'teeth are made may be termed a highfusing dental porcelain -9, asusually provided, may also be provided in plate or base is made isbetweenporcelain and glass, probably being closer to glass than toporcelain. The denture base ceramic body which has been developed andwhich produces a thermal expansion and contraction curve, such as thatmarked in Figure 1 of the drawings Denture base ceramic body has thefollowing formula:

Per cent Feldspar 65 to 80 Amorphous silica 10 to 20 Borax glass 5 to 15In the ceramic bodies of both the tooth and denture base we haveutilized amorphous sihca for the following reasons:

1. It produces a low coeflicient of expansion bodies of the foregoingformulae will expand and contracgin substantial harmony.

In carrying out the process of forming our improved denture the teethare moulded and fired in the usual way. A model It! made from theinvestment material and exactly duplicating in' size andform the area tobe covered by the denture base is cast, and this is invested in theinvestment material II in the usual manner in the lower half l2 of aflask. Suitable escapeways carrying out this process. On this model H1is a temporary denture base l3 composed of material which can' bereadily melted and whichhas the artificial teeth l4 set therein. Thistemporary denture base I3 is identical in form with the permanentdenture base to be produced. (See Figures 3 and 4.) The lower half ofthe flask then has a liner or gasket l6 placed on its upstandingperipheral edge, and the upper half ll of the flask separated from thelower half by this liner. Investment material I8 identical with thematerial II and with the material of the model 10 is then poured inthrough openings in the top of the upper half I! of the flask until thesame is completely filled. (See Figure 5.) After the investment materialin the upper half l'l has set or hardened so as to secure the artificialteeth therein the flask may be inverted, heated or boiled, its partsseparated, and the temporary denture base melted or washed out. Thisalso washes the material from the escapeways 9. Fig. 6.) The liner I6,which formerly separated the halves of the flask, is then removed andthe novel ceramic body 19 of the denture base filled into the spaceformerly occupied by the a low fusing bas'e ceramic body which are in(See' and contraction curve of feldspar is shown in Figsubstantialharmony in expansion and contraction, certain practical advantages areobtained by having the denture base ceramic body fused around 700 to 800F. lower than the tooth ceramic body. For example, there is no dangerofthe pre-formed tooth being deformed by a heat too close to itssoftening temperature. The temperature cited will not aflect stains orother markings placed on the face of the teeth to achieve certainartistic effects. The type of investment used to form the denture platesneed not be excessively high fusing. The furnace for fusing the plateceramic body to the teeth need not be intricate or expensive. The metalflask just above described in which the fusing is acthe particular mouthfor which it is designed, so

the denture plate must be formed while plastic over an exact model ofthe particular month. This is the mqlel shown in Figures 3 to 801 thedrawings, and must be made of an investment composition which has athermal contraction in agreement and harmony with the contractions ofboth the tooth ceramic body and denture base or plate ceramic body inorder that no checking or fracturing of the teeth'or plate" shall occurin the cooling process.

Dental investment compositions generally'con-- tain a considerableportion of quick setting material, such 'as gypsum, or plaster of Paris,together with siliceous materials such as silicasand and fire clay grog.

In the drawings, Figure 2 shows a thermal ex- .pansion-curve of aninvestment material having 20% plaster of Paris and 80% silica grog.That same figure shows another thermal expansion curve ofan investmentmaterial having 25% plaster of Paris and 75% silica sand. The thermalexpansion curve of gypsum-silica mixtures as shown is generallycharacterized by certain sharp breaks dueto silica inversions and todehydration of the sulphate. It has been shown in Figure 1 that thethermal expansion and contraction curves of the new tooth ceramic bodyand of the new denture base ceramic body have been brought intopractical conformity whereas the curves of the commercial investmentmat'erialsshown in Figure 2 are widely divergent from the curves of thetooth and base ceramic materials, the former of which is also shown inFigure 2. A denture base formed in investments such as those indicatedas commercial would be bad-- ly cracked when cooled.

We have found that feldspar has a very uniform curve of expansion. Athermal expansion we 2. We have further found that an investmentcompound of the following general proportions will give a thermalcontraction curve in substantial harmony with the curves of the toothand denture base ceramic bodies hereinbefore described. The formula forthis investment material is as follows:

Per cent v A form of calcium sulphate (Hydrocal) 10 to 25 Felclspar p 30to Silica gr g I 10 to 45' The thermal contraction curve of thisinvestment material is shown in Figures 1 and 2.

In Figure 2, we, therefore, find that through the critical range whichwe have before discussed,

the linear thermal contractions of the tooth ceramic'body, the denturebase ceramic body and the investment material are always controlled soas to never vary one from the other more than one-half of one thousandthof an inch per hnear inch.

After the denture base ceramic body 19 has been placed in the recessformerly occupied by the temporary denture base and the flask sectionsre-united, the flask is then placed in a kiln and" the temperaturegradually raised to the softening temperature of the denture baseceramic body whereupon pressure is preferably added to the top of theflask to accelerate the coming together of the sections of the flask.(See Fig-8.) This may be-accomplished by merely placing a weight of afew pounds on the upper flask section. It, of course, will bereadilyseen that the upper part of the flask will by its weight or by gravitycome into contact with the lower part of the flask when the denture baseceramic body becomes soft, but the weight will hasten that step andallow for cutting off the heat to the kiln. Adding the weight orpressure tothe upper part of the flask saves time and fuel, and

permits the temperature from goingbeyondthe f necessary temperature tosoften the denture base ceramic body.

Among the advantages of the invention are its effective employment inpartial plates, the preservation, and prevention of fading of, a naturalgum pink color, the freedom from warpage, the imperviousnesstoinfiltration of mouth acids, and therefore its ability to remain .cleanand free from odors, its pleasant feeling on the oral tissues, thebetter adaptation to, and fitting of, these tissues, and the removal ofthe danger of the teeth dropping therefrom.

Of course, the denture base material may be modified in various wayswithout departing from the invention set forth and described in theappended claims.

The invention is hereby claimed as follows:

1. A denture base ceramic body for attachment in fused relation to atooth ceramic body, said base ceramic body containing substantially 65to 80 per cent feldspar, 10 to 20 per cent amorphous silica and 5 to 15per cent borax glass, and said base comprising said ingredients in suchproportions that the thermal contractions of said bodies through a rangeextending at least from the freezing point of the base toatmospherictemperature are in substantial harmony, said base having afusing point of from approximately 15oo to 1600 Fahrenheit. 1 2. Adenture base ceramic body for attachment in fused relation to a toothceramic body, said base ceramic body containing substantially 65 to 80percent feldspar, 10 to 20 per cent amorphous silica and 5 to 15 Percent borax glass, and said base comprising said ingredients in suchproportions thatthe thermal contractions of said bodies through a rangeextending from the freezing point of the base to atmospherlc temperaturevary less than .001 inch per linear inch and are in substantialharmony,said base having a fusing point of from approximately1500 to 1600Fahrenheit.

3. A denture base ceramic body of relatively low fusing temperature formoulding attachment to an artificial tooth body of high fusingtemperature in cooperation with a body of investment material to form a.unitary ceramic denture, said base comprising substantially 65 to 80 percent feldspar, to 20 per cent amorphous in fused relation to a toothceramic wdy comprising 70 to 90 per cent feldspar and 10' 1:030

silica and 5 to per cent borax glass, whereby said base has a. fusingpoint of from approximately 1500? to 1600 Fahrenheit and its thermalcontraction from its freezing point to room temperature is insubstantial harmony with the thermal contractions of, said tooth andinvestment bodies.

4. A denture base ceramic body of relatively low fusing temperature formoulding attachment to an artificial tooth body of high fusingtemperature in cooperation with abody of investment material to form aunitary ceramic denture, said base comprising substantially 65 to 80 percent feldspar, 10 to per cent amorphous silica and 5 to 15 per centborax glass, whereby said base has a fusing point of from approximately1500 to 1600 Fahrenheit and its thermal contraction from its freezingpoint to room temperture varies less than .001 inch per-linear inch fromthe thermal contractions of the tooth and investment bodies.

5. A denture base ceramic body for attachment per cent amorphous silica.said base ceramic body comprising to 80 per cent feldspar,, 1ii to 20per cent amorphous silica and 5 to 15 per cent borax glass, and saidbase comprising said ingredients in such proportions that the thermalcontractions of said bodies through a range extending at least from thefreezing point of the base to atmospheric temperature are in substantialharmony.

6. The method of providing a denture base ceramic body adapted to befused to an artificial tooth ceramic body comprising to 90per centfeldspar and 10 to 30 per cent amorphous silica, said tooth ceramic bodyhaving a predetermined thermal contraction curve and a relatively higherfusing temperature than the denture base ceramic body, said methodcomprising the steps of providing a denture base ceramic body comprising65 to per cent feldspar, -10 to 20 per cent amorphous silica, and 5 to15 per cent borax glass, and proportioning the ingredients of thedenture base ceramic body so that the thermal contraction curve of thebase ceramic body will substantially correspond to the thermalcontraction curva of the tooth ceramic body at least from the fusingtemperature of the base ceramic body to atmospheric temperature.

PYUNGTOO WILLIAM LEE. CHARLES DIE'IZ.

